The overall aim of this project is to determine the biological significance of small nucleic acids (SNAs) in Leishmania. CD1, which is an episome that occurs in some Leishmania either as a circular DNA or integrated into chromosomal DNA will be the primary focus of the project. Inducible SNAs in L. tarentolae will also be studied as a model of DNA sequence mobilization and chromosome copy number control and a RNA virus will be characterized as a secondary priority. The nucleotide sequence of the 29 kb CD1 circular monomer will be determined to elucidate its genetic content and organization. Circular CD1 from different stocks will be compared as will the integrated CD1 to identify essential and nonessential sequences. The functional organization of CD1 will be determined by transcript mapping. These experiments will identify protein coding genes, intergenic sequences, the general characteristics of the transcriptional and RNA processing units and potential promoters and replication origin. The CD1 linearization site and chromosomal integration sites will be identified and characterized in order to elucidate CD1 integration and excision. The related processes of chromosome mobilization and SNA amplification will be examined in a L. tarentolae strain that reproducibly creates SNA and varies its copy number in response to nutritional conditions. A stable molecular cloning vector that will be valuable for functional studies will be developed from CD1 using information gained as described above. The nucleotide sequence of the 6 kb LR1 viral genome will be determined and its protein products will be identified and characterized. These studies are designed to elucidate the coding function of this genome and the consequence to Leishmania of infection of the virus.